You might think that if the National Security Agency were tapping the phones of dozens of world leaders, President Obama would be aware of this fact. Apparently not—according to a Wall Street Journal report last night, the NSA's spy operations are so extensive that not even the president of the United States knows about all of them.

Based on interviews with US officials, the paper said that "President Barack Obama went nearly five years without knowing his own spies were bugging the phones of world leaders. Officials said the NSA has so many eavesdropping operations under way that it wouldn’t have been practical to brief him on all of them."

NSA monitoring of German Chancellor Angela Merkel and 34 other world leaders was revealed to the White House after an internal Obama administration review that started this summer. The NSA stopped its spying of some world leaders, but it's not clear how many.

"The White House cut off some monitoring programs after learning of them, including the one tracking Ms. Merkel and some other world leaders, a senior US official said," according to the Journal. "Other programs have been slated for termination but haven’t been phased out completely yet, officials said."

While the president "was briefed on and approved of broader intelligence-collection 'priorities,'" decisions to monitor specific targets were made by the NSA. The practice of making those decisions at the NSA is under review.

This does not mean that the US has stopped spying on world leaders. "The administration didn’t end all operations involving world leaders following this summer’s revelations because some of the programs are producing intelligence of use to the US," the Journal reported. "It could not be learned Sunday how many of the eavesdropping operations were stopped, or who is on the list of leaders still under surveillance."

Since world leaders talk to each other, removing one from direct surveillance doesn't remove all of their communications from NSA ears. "While Ms. Merkel and some world leaders are no longer being monitored, for instance, the US may still be monitoring many of their foreign counterparts," the report said. "So communications involving some leaders who aren’t directly subject to US monitoring still may be swept up by the NSA, officials said."

The report called this the "US government’s first public acknowledgment that it tapped the phones of world leaders."

The acknowledgement comes after The Guardian newspaper revealed the monitoring of 35 world leaders last week based on a classified document leaked by Edward Snowden. Also today, German magazine Der Spiegel published an investigative report noting that US intelligence officials "used the American Embassy in Berlin as a listening station."